CLINICAL CORE: ABSTRACT The Pacific Northwest Udall Center (PANUC) Clinical Core has recruited and characterized a cohort of more than 600 individuals with Parkinson's disease (PD) during the inaugural award. Data from the PANUC Clinical Core, in collaboration with other Udall Centers and other academic medical centers, have helped confirm Apolipoprotein E (APOE) and glucocerebrosidase (GBA) as genes that are relevant to the pathogenesis of cognitive decline in PD. Understanding the mechanisms underlying these gene effects is the focus of this renewal application, utilizing brain autopsy and genomic approaches (Project 1), neuroimaging (Project 2), and quantitative balance and gait (B&G) measurements (Project 3). The Clinical Core will provide longitudinal data for subjects in all 3 projects, and will provide well-characterized PD and control subjects of appropriate genotypes for Projects 2 and 3. B&G testing has been added to the test battery as an innovation that is thought to reflect higher order CNS function closely related to cognition. This innovation leverages the expertise of Dr. Fay Horak, an investigator introduced to PANUC by way of PANUC pilot award funding. As in the first cycle, Clinical Core subjects will be followed at two sites: one in Portland directed by Clinical Core Leader Dr. Joseph Quinn, and the other in Seattle directed by Clinical Core Co-Leader Dr. Shu-Ching Hu.